Biological fluid filtration method and apparatus

ABSTRACT

A biological fluid processing or fluid filtration system is provided having novel open and closed loop processing systems wherein the gases transferred into and out of the system during processing pass through a porous medium in upstream and/or downstream gas inlet or outlet housings or vents in a manner which precludes the fluid being processed or filtered from ever contacting the housings or vents. Each housing or vent is separated from the fluid by a column of gas in its respective transfer line. The upstream gas inlet housing or vent is in communication with the unfiltered biological fluid, and the downstream gas inlet housing or vent is in communication with the filtered biological fluid.

CROSS REFERENCE TO RELATED APLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/164,668, filed on Jun. 7, 2002, now U.S. Pat. No. 6,802,425,which is a divisional application of U.S. application Ser. No.09/688,999, filed Oct. 16, 2000, which is now U.S. Pat. No. 6,427,847,which is a divisional application of U.S. application Ser. No.09/272,203, filed Mar. 19, 1999, which is now U.S. Pat. No. 6,171,493.U.S. application Ser. No. 10/164,668, U.S. Pat. No. 6,427,847, and U.S.Pat. No. 6,171,493 are each hereby incorporated by reference as if setforth in their entirety herein. U.S. application Ser. No. 10/164,668 waspending as of the filing date of the present application.

U.S. application Ser. No. 09/272,203, from which priority is claimedabove, claims the benefit, Under 35 U.S.C. 119 (e), of provisionalapplication No. 60/078,848, filed Mar. 20, 1998, and of provisionalapplication No. 60/083,484, filed Apr. 29, 1998. The provisionalapplication 60/078,848 and 60/083,484 are hereby incorporated byreference as if set forth in their entirety herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for processingbiological fluids into their therapeutically valuable components. Moreparticularly, the present invention relates to a method and apparatusfor processing donated blood into its therapeutically valuablecomponents. Most particularly, the present invention relates to animproved method and apparatus for processing donated blood into itstherapeutically valuable components which uses improved open-loop andclosed-loop systems to substantially increase the recovery of all theblood products from the donated blood.

2. Discussion of the Related Art

Methods and apparatus for processing blood are well known in the priorart. U.S. Pat. No. 3,892,236 to Djerassi shows an apparatus for thecontinuous withdrawal of blood from a human donor, forced extracorporealcirculation of blood of the donor with separation of granulocytes, andreturn by gravity of the leukocyte-poor whole blood to the donor.

U.S. Pat. No. 5,126,054 to Matkovich shows a venting means for ventinggas from the transfer line of a liquid delivery system comprising ahousing, a first, liquid-wettable, microporous membrane carried in saidhousing so as to be in communication with the transfer line, and asecond, non-liquid-wettable, gas permeable microporous membranesuperimposed on said microporous membrane to the outward side of thehousing. Gas in the delivery system is vented from the system so long asthe first microporous membrane remains unwetted by the delivery liquid.

U.S. Pat. No. 5,451,321 to Matkovich shows biological fluid processingassemblies having a gas inlet, and/or a gas outlet.

While these devices are generally satisfactory, some of the methods andapparatus of the prior art leave a large amount of biological fluidtrapped in various elements of the fluid processing apparatus. While theaforementioned patent U.S. Pat. No. 5,451,321 to Matkovich provides forliquid trapped in various elements of the blood processing system to berecovered either by causing a volume of gas behind the entrapped liquidto push the liquid through those elements and into the designatedcollection bag, or by pulling the entrapped liquid into the designatedcollection bag by a pressure differential (e.g. gravity head, pressurecuff, suction and the like), the system still has several drawbacks. Onedrawback is that they require one or more nonwettable, gas permeable,membranes. This requirement can lead to increased costs over wettablemembranes.

Therefore, those skilled in the art continue to search for a method andapparatus to provide for optimal recovery of the biological fluid frombiological fluid processing systems, cost reduction and ease of use, andhave developed novel open and closed loop systems and methods associatedtherewith to achieve this goal.

SUMMARY OF THE INVENTION

The problems of the prior art are solved by the present inventionutilizing novel open and closed loop biological fluid processing systemswhich all share the concept that the gases transferred into, out of, orwithin the biological fluid processing system have the transfer linesarranged or configured in a manner which precludes the biological fluidfrom ever contacting the upstream and downstream gas inlet or outlethousings or vents, or bypassing the fluid filtration or leukocytedepletion device. Gases are transferred into and out of the biologicalfluid processing systems through a porous medium in the upstream anddownstream gas inlet housings or vents.

Each housing or vent is separated from, and in communication with thebiological fluid by a column of gas in the transfer lines. The upstreamgas inlet housing or vent is in communication with the unfilteredbiological fluid and the downstream inlet or vent is in communicationwith the filtered biological fluid.

In one embodiment of the present invention, a biological fluidfiltration apparatus is provided which includes a fluid filtration orleukocyte depletion device having an inlet and an outlet, a fluidcontainer upstream from and elevated above said fluid filtration orleukocyte depletion device and having an outlet, a first conduit influid communication with the outlet of said fluid container and theinlet of said fluid filtration or leukocyte depletion device, areceiving container downstream of said fluid filtration or leukocytedepletion device and having an inlet, a second conduit in fluidcommunication with the inlet of said receiving container and the outletof said fluid filtration or leukocyte depletion device, an upstream gasinlet having one of its□ ends elevated above said fluid container, andhaving its other end in fluid communication with said first conduit, anda downstream gas inlet having one of its' end elevated above said fluidcontainer, and having its' other end in fluid communication with said orleukocyte depletion or fluid filtration device.

In another embodiment of the present invention, there is provided aclosed loop fluid filtration or leukocyte depletion device including afluid filtration or leukocyte depletion device having an inlet and anoutlet, a fluid container upstream from, and elevated above, said fluidfiltration or leukocyte depletion device and having an outlet, a firstconduit in communication with the outlet of said fluid container and theinlet of said fluid filtration or leukocyte depletion device, areceiving container downstream of said fluid filtration or leukocytedepletion device and having an inlet, a second conduit in fluidcommunication with the inlet of said receiving container and the outletof said fluid depletion device and a bypass line in fluid communicationwith said fluid container and said receiving container and having a loopportion elevated above said fluid container.

In yet another embodiment of the present invention the upstream gasinlet is eliminated and the downstream gas inlet is connected to thereceiving container instead of the fluid filtration or leukocytedepletion device.

In another embodiment of the present invention, the downstream gas inletmay be eliminated.

In still another modification of the present invention, the upstream gasinlet housing or vent and the downstream gas inlet housing or vent maybe part of the same inlet device.

Thus, it is an object of the present invention to provide an improvedmethod and apparatus for filtering biological fluids.

It is a further object of the present invention to provide an open gasvent that prevents premature gas introduction into the fluid stream in abiological fluid processing system.

It is a further object of the present invention to provide an open loopbiological fluid processing system with transfer lines or conduitsarranged or configured in a matter which precludes the biological fluidfrom contacting the upstream and downstream gas inlet housings or vents,or bypassing the biological fluid depletion device.

Another object of the present invention is to offer a wider choice ofmaterials which may be used in the gas inlet housings or gas outlethousings or vents of biological fluid filtration systems. The presentinvention does not require wettable membranes. The choice of membranesfor the present invention is not limited.

Another object of the present invention is to provide a system of theforegoing nature where gas is transferred into and out of the biologicalfluid processor through porous medium in the upstream and downstream gasvents.

A still further object of the present invention is to provide an openloop system of the foregoing nature where each gas vent is separatedfrom, and in communication with the biological fluid by a column of gasin the transfer lines or conduits.

A still further object of the present invention is to provide an openloop biological fluid filtration system of the foregoing nature whereinthe upstream gas inlet housing or vent, and the downstream gas inlethousing or vent may be a portion of the same inlet device.

A still further object of the present invention is to provide a closedloop biological fluid filtration system having a bypass line bypassingthe biological fluid filtration device, the bypass line is arranged suchthat a column of gas separates the unfiltered biological fluid upstreamof the filtration device from the filtered biological fluid downstreamof the biological fluid filtration device.

A further object of the present invention is to provide an open loopbiological fluid filtration system having an upstream gas inlet elevatedabove the level of the biological fluid container and having a satellitebag connected to the biological receiving fluid container.

Further objects and advantages of the present invention will be apparentfrom the following description and appended claims, reference being madeto the accompanying drawings forming a part of the specification,wherein like reference characters designate corresponding parts in theseveral views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a prior art biological fluid filtrationsystem.

FIG. 2 is an elevational view of a construction embodying the presentinvention.

FIG. 3 is an elevational view showing a modification of the constructionshown in FIG. 2.

FIG. 4 is an elevational view of a further modification of theconstruction shown in FIG. 2.

FIG. 5 is an elevational view showing a further modification of theconstruction shown in FIG. 2.

FIG. 6 is an elevational view of a closed loop construction embodyingthe present invention.

FIG. 7 is an elevational view showing a modification of the constructionshown in FIG. 6.

FIG. 8 is an elevational view of a further modification of theconstruction shown in FIG. 6.

FIG. 9 is an elevational view showing a further modification of theconstruction shown in FIG. 6.

FIG. 10 is an elevational view showing a further modification of theconstruction shown in FIG. 6.

FIG. 11 is an elevational view showing a further modification of theconstruction shown in FIG. 6.

FIG. 12 is an elevational view of a construction embodying the presentinvention utilizing a satellite bag.

FIG. 13 is a perspective view of a biological fluid filter constructionembodying the present invention;

FIG. 14 is a front elevational view of the construction shown in FIG.13;

FIG. 15 is a sectional view, taken in the direction of the arrows, alongthe section line 15-15 of FIG. 14;

FIG. 16 is a sectional view, taken in the direction of the arrows, alongthe section line 16-16 of FIG. 14

FIG. 17 is a sectional view, taken in the direction of the arrows, alongthe section line 17-17 of FIG. 14;

FIG. 18 is a front elevational view of the inlet portion of theconstruction shown in FIG. 13;

FIG. 19 is a rear elevational view of the construction shown in FIG. 18;

FIG. 20 is a front elevational view of the outlet portion of theconstruction shown in FIG. 13;

FIG. 21 is a rear elevational view of the construction shown in FIG. 20;

FIG. 22 is a modification of the construction shown in FIG. 13;

FIG. 23 is a diagrammatic view of the filter medium shown in theconstruction of FIG. 22;

FIG. 24 is a diagrammatic view of a further modification of theconstruction shown in FIG. 13; and

FIG. 25 is a diagrammatic view of the filter medium shown in theconstruction shown in FIG. 24.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The aforementioned U.S. Pat. No. 5,451,321 to Matkovich shows abiological fluid processing assembly for filter biological processessuch as blood. An example of the Matkovich apparatus is illustrated inFIG. 1. The apparatus has a blood collection bag 30 connected by a firstconduit 31 to a leukocyte depletion device 32. The leukocyte depletiondevice 32 is connected by a second conduit 33 to a blood receiving bag34. A gas inlet 35 having a cover or cap 36, is provided in fluidcommunication with the first conduit 31 downstream of said collectionbag 30, and a gas outlet 37 is provided in second conduit 33 downstreamof the leukocyte depletion device 32.

In one embodiment of the prior art, a first clamp 38 is placed on firstconduit 31 downstream of the blood collection bag 30 and upstream of thegas inlet 35, and a second clamp 39 is placed on the second conduit 33downstream of the gas outlet 37. In a typical operation the bloodcollection bag 30 is sterile and is connected to the conduit 31 asillustrated. The gas inlet 35 is comprised of a housing 41 and a porousmedium barrier 42 in addition to cover or cap 36. Additional details ofthe barrier 42 may be obtained by reference to U.S. Pat. No. 5,451,321.

Prior to the start of blood processing, the inlet clamp 38, the outletclamp 39, and the gas inlet 35 are all closed. The blood processing isinitiated by opening the inlet clamp 38, and allowing the blood to drainfrom the blood collection bag 30. A column of blood flows through thefirst conduit 31 into the leukocyte depletion device 32 displacing anygas within the blood processing system. No blood enters the gas inletdevice 35 since the gas inlet is closed. The displaced gas is expelledfrom the system through the gas outlet 37 since the second clamp 39 isclosed. As substantially all the gas is expelled from the first conduit31 and the portion of the second conduit 33 leading to the gas outlet37, the porous medium is wetted by the blood, and the blood flow seizesor stops at the liquiphobic bearer in the gas outlet 37.

Once the gas outlet 37 is wetted, the second or outlet clamp 39 isopened, and filtered blood flows into the blood receiving bag 34. Thegas outlet 37 need not be closed prior to opening of the outlet clampsince the gas outlet is sealed by the wetted porous medium. Blood flowsfrom the collapsible blood container or bag 30 through the leukocytedepletion device 32 and into the blood receiving bag 34 untilequilibrium is reached within the system and blood ceases to flow. Atthis point, all of the blood has not been processed through theleukocyte depletion device 32. The first conduit 31, the filter device32, and the second conduit 33 are filled with blood.

Removing the cover or cap 36 from the gas inlet 35 allows gas to enterthe processing system and drive the blood through the leukocytedepletion device 32. However, since the filter medium 32A within theleukocyte depletion device 32 is wetted, the flow of blood seizes whengas fills the upstream chamber of the filter. When the blood flowseizes, the second or outlet clamp 39 is closed.

It can be seen that, at this point, the downstream side of the leukocytedepletion device 32, and the entire second conduit 33 are filled withblood. With ever increasing need for blood and blood products, thoseskilled in the prior art have strived to increase the recovery of blood,and such a relatively large quantity of blood being left in the deviceof the prior art is no longer satisfactory.

In order to solve the recovery problems present in the prior artdevices, the open-loop construction shown in FIG. 2 has been developed.There is shown a biological fluid filtration system 44 having aleukocyte depletion device 45 with a filter medium 46, an inlet 47, andan outlet 48. The leukocyte depletion device may be such as thebiological fluid filter shown in provisional application Ser. No.60/083,484, which has been incorporated herein by reference, or anyother suitable fluid filtration or leukocyte depletion device.

A blood container 49 is provided upstream from, and elevated above saidleukocyte depletion device 45. Blood container 49 is connected to, or influid communication with, said leukocyte depletion device 45 throughfirst conduit 50.

There is also provided a blood receiving container 52 downstream of saidleukocyte depletion device 45. Leukocyte depletion device 45 isconnected to blood receiving container 52 through second conduit 54. Anupstream gas inlet 56 is provided in fluid communication with said firstconduit 50, and a downstream gas inlet 58 is provided in fluidcommunication with said leukocyte depletion device 45, downstream ofsaid filter medium 46.

An inlet clamp 60 and an outlet clamp 61 may be provided. It should beunderstood that one or more of inlet clamp 60 and/or outlet clamp 61 maybe provided, and be well within the scope of the present invention.

Upstream gas inlet 56 may take the form of a vent line 62 beingconnected to an upstream gas inlet housing 64. Vent line 62 may have aU-shaped portion 62A to prevent drawing of gas into biological fluidfiltration system 44 until substantially all of the biological fluid hasdrained from the biological fluid container 49. The other end of ventline 62 should be at a sufficient height such that it is alwayspositioned above the level of the fluid in the biological fluidcontainer 49.

Upstream gas inlet housing or vent 64 has an inlet 65 and an outlet 66.Interposed between the inlet 65 and the outlet 66 in a sealingrelationship is at least one layer of a porous medium 67. The porousmedium may be such as a bacterial retention medium, a viral retentionmedium, or other suitable medium.

In a similar manner, the downstream gas inlet 58 may comprise a secondvent line 70 connected to a downstream gas inlet housing or vent 71having an inlet 72 and an outlet 73. A cap or other closure 74 may beused in connection with the opening and the closing of inlet 72.Interposed in the housing 71, between the inlet 72 and the outlet 73 isa second porous medium 76. The second porous medium 76 may also be suchas a bacterial retention medium, a viral retention medium, or othersuitable medium.

As illustrated, upstream gas inlet housing 64 and downstream gas inlethousing 71 may be provided in a single novel inlet device 80 having abarrier or wall 81 which prevents fluid communication between theupstream gas inlet porous medium 67 and the downstream gas inlet porousmedium 76. The upstream medium 67 and the downstream medium 76 may thenbe formed of a single sheet.

The upstream gas inlet 56 and the downstream gas inlet 58 may be placedin any practicable location as long as they are located such that theblood product being filtered never contacts the porous medium 67. In thepreferred embodiment illustrated the porous medium 67 contained withinthe housing 64 is elevated above the blood container 49, but otherlocations are well within the scope of the present invention.

In the method of blood processing embodying the present invention, theinlet clamp 60 and the outlet clamp 61 are initially closed. The cap orclosure 74 covering the inlet 72 of downstream gas inlet device,housing, or housing portion 71 is also in place.

The blood processing is initiated by opening the inlet clamp 60 andallowing the biological fluid to flow through the first conduit 50. Asthe fluid flows past the junction 50A, some of the fluid will flow intothe upstream gas inlet 56 through vent line 62. A column of liquid of apredetermined, desired, length (shown as dimension A in FIG. 2), betweenthe junction 50A and the bottom of the loop portion of 62A, prevents gasentry into the system until substantially all of the biological fluidhas been drained from the biological fluid container 49.

The upstream gas vent may be thought of as a manometer measuring thepressure at the junction 50A. As the level of fluid within thebiological fluid container 49 decreases, the pressure at the junction50A decreases and, therefore, the height of the fluid in the vent line62 decreases. When substantially all of the biological fluid has drainedfrom the biological fluid container 49, the atmospheric pressure actingon the column of fluid within the vent line 62 will cause all of thefluid within the upstream gas inlet 56 to drain into the conduit 50. Theremaining fluid contained with the upstream gas inlet line 62 is drainedinto the conduit 50 because the upstream gas inlet is open toatmosphere. Thus, dimension A in FIG. 2 must be of sufficient distancesuch that the above described sequence of events occur. At this point,the leukocyte depletion device 45 downstream of the filter medium 46 andthe second conduit 54 between the leukocyte depletion device 45 and theblood receiving container 52, are all filled with filtered biologicalfluid.

The filtered biological fluid or blood downstream of the filter medium46 in the leukocyte depletion device 45 may now be recovered by openingthe cap or closure 74 covering the inlet 72 of downstream gas inletdevice, housing, or housing portion 71. In place of cap 74, a clamp (notshown) could be used on second vent 70.

After this step substantially all of the blood previously unrecovered bythe prior art devices is in the blood receiving container 52. Any gas inthe receiving container 52 and/or second conduit 54 downstream of thedisconnecting point of the blood receiving container 52 may be pushedback up into the second conduit 54 by gently squeezing the bloodreceiving container 52, and then the outlet clamp 61 can be closed.

As is now evident, the construction shown in FIG. 2 provides an easymethod of drainage of substantially all of the biological fluid from thereceiving bag 52 through the leukocyte depletion device 45. In addition,the biological fluid filtration system 44 in its preferred embodimentutilizes only a single housing in the inlet device 80, and a singlelayer of porous medium and substantially all of the filtered biologicalfluid is recovered. The system has a lower number of parts, is easier tomanufacture, and recovers more biological fluid at a lower per unitbiological fluid processing cost.

Alternate embodiments of the construction shown in FIG. 2 areillustrated in FIGS. 3-5, with like numerals designating correspondingparts in the several views. Their operation can easily be understood bythose skilled in the art in view of the foregoing description.

A modification of the present invention utilizing only the upstream gasinlet 56 and a satellite bag 83 is shown in FIG. 12. Satellite bag 83 isconnected in fluid communication with blood receiving container 52 bysatellite conduit 84. Satellite clamp 85 opens and closes satelliteconduit 84. In this embodiment of the present invention, the satellitebag is used to vent the gas displaced from the receiving container 52.The volume of the satellite bag 83 should be sufficient to accept all ofthe gas displaced. After all the blood has flowed into the receivingcontainer 52, the container is gently squeezed until all of the gas isvented past the satellite clamp 85, at which time the satellite clamp 85is closed.

Referring now to FIG. 6, there is shown a closed loop biological fluidfiltration system 90. As in previous embodiments of the presentinvention, there is a leukocyte depletion device 45 having a filtermedium 46, an inlet 47, and an outlet 48. The filter medium 46 isinterposed in a sealing relationship between the inlet 47 and the outlet48. The system 90 also includes a blood container 49 connected by firstconduit 50 to the inlet 47 of leukocyte depletion device 45. Inlet clamp60 is provided as before.

Provided downstream of the leukocyte depletion device 45 is a bloodreceiving container 52. A second conduit 54 is connected between theoutlet 48 of the leukocyte depletion device 45 and the inlet of theblood receiving container 52. Used in place of the upstream gas inlet 56and a downstream gas inlet 58 is a by-pass line 91, which may be openedand closed by by-pass clamp 92. A first end of the by-pass line 91 isconnected in fluid communication with the blood container 49 proximatethe outlet thereof, and the other end of the by-pass line 91 isconnected in fluid communication with the blood receiving container 52proximate the inlet thereof. The loop portion 93 of the by-pass line 91is positioned such that when the blood container 49 is full of blood,the blood will not reach the loop portion 93 and thus, there can be noflow of blood through the by-pass line. One such position is illustratedin FIG. 6 with the loop portion 93 elevated above the blood container49.

In place of loop portion 93, a one way check valve or other device maybe used such that a column of gas will always separate the unfilteredbiological fluid upstream of the filtration device from the filteredbiological fluid downstream of the leukocyte depletion device 45. Thepositioning of the loop portion 93, and the bypass line 91 may also bevaried to accomplish this.

The method of operating the closed loop embodiment of the inventiondiffers in several respects from the method used with the open loopembodiment. As illustrated in FIG. 6, the additional by-pass clamp 92 isneeded because no gas inlet or gas outlet devices are provided, as werenecessary in the prior art. Prior to the start of blood processing, theinlet clamp 60 is closed and the by-pass clamp 92 is open. The bloodprocessing is initiated by opening the inlet clamp 60 and allowing bloodto drain from the blood container 49 through first conduit 50 into theleukocyte depletion device 45 and therethrough to the blood receivingcontainer 52. The blood does not by-pass the leukocyte depletion device45 because of the loop portion 93 of the by-pass line 91 being elevatedto a sufficient height. The gas within the closed loop biological fluidfiltration system 90 is displaced by the blood flow into the bloodreceiving container 52. As the blood container 49 approaches its nearlyempty condition, the gas stored within the receiving container 52automatically flows through the by-pass line 91 into the blood container49 and allows substantially all of the blood to be processed through theleukocyte filtration device 45. It is important to note that the chamberof the leukocyte depletion device 45 downstream of the filter media 46at this point will be filled with blood, as will the second conduit 54between the leukocyte depletion device and the blood receiving container52. If there is any gas left in the receiving container 52 it may bedisplaced into the by-pass line 91 by closing the outlet clamp 61,gently squeezing the blood receiving container 52 and closing theby-pass clamp 92. In this embodiment of the invention comprising theclosed loop biological fluid filtration system, the chamber downstreamof the filter medium 46 in the leukocyte depletion device 45 is notdrained of blood, nor is second conduct 54. However, the inlet deviceand the outlet devices of the prior art are eliminated, and a simplifiedsystem is provided.

Additional modifications of the closed loop biological fluid filtrationsystem 90 are shown in FIGS. 7-11. Their operation can be understood bythose skilled in the art from the foregoing description.

A more detailed description of the biological fluid filter can be had byreferring to FIGS. 13-25. The biological fluid filter 100 consists of aninlet section 101 and an outlet section 102. Referring to FIGS. 14 and15, the inlet section 101 of biological fluid filter 100 has an inlet103, including port 103A, communicating with first passage 104, which isin fluid communication with first or inlet chamber 105 through firstport of outlet 104A. Further, biological fluid filter 100 has a secondpassage 106 in fluid communication with both, first or inlet chamber105, and first vent chamber 107.

The outlet section 102 has a second vent chamber 110 in fluidcommunication with a third passage 111. Third passage 111 is in fluidcommunication with outlet 112 through port 112A. A fourth passage 113 isin communication with the third passage 111 and the second or outletchamber 115. A vent filter element 117 separates the first vent chamber107 from the second vent chamber 110, and is held in place by means tobe described in more detail hereinbelow.

Similarly, a biological filter element 119 separates the first or inletchamber 105 from the second or outlet chamber 115. Both the vent filterelement 117 and the biological filter element 119 may consist of one ormore layers, and be made of a wide variety of filter materials. In theembodiment illustrated, they are liquiphilic.

In the preferred embodiment, the vent filter element 117, and thebiological fluid filter element 119, are made of the same filter medium,which may be such as glass or nylon fibers. In use, a fluid container(not shown), such as a blood container is placed in fluid communicationwith inlet port 103A. Similarly, a biological fluid receiving bag (notshown) is placed in fluid communication, by means well known in the art,with outlet port 112A. Fluid flow is initiated and blood flows in theinlet port 103A, through the first passage 104 and through first outlet104A into inlet chamber 105.

In operation, as the blood enters the inlet chamber 105, the blood maywick into the filter element 119. The blood may wick into the filterelement 119 faster, or slower, than the blood level rises in the firstor inlet chamber 105. The rate at which the blood wicks into the filterelement 119 will depend on the properties of the filter medium beingchosen, and the biological fluid being filtered. These propertiesinclude the pore size of the medium, the density of the biologicalfluid, the surface tension of the biological fluid, and the contactangle of the solid-liquid-gas interface. While the blood level is risingin the inlet chamber 105, any air entrapped in chamber 105 is eitherpassing through a portion of the filter element 119 which is not yetwetted, or is proceeding through second passage 106 and being vented outthe vent filter element 117.

As the blood level continues to rise in inlet chamber 105, at somepoint, the biological filter element 119 will be sufficiently “wetted”,and the biological fluid being filtered will “breakthrough” the filterelement 119, and will start flowing into outlet chamber 115. The fluidbreakthrough depends on the pore size of the material, the surfacetension and the contact angle, as well as the pressure differentialacross the filter element 119.

Due to the pressure differential across the biological filter element119, the biological fluid continues to flow up into second passage 106.If the pressure differential is sufficient, the biological fluid willcontact the vent filter element 117, which is the preferred embodiment.If the vent filter element 117 is also made of a liquiphilic media, itwill become “wetted out”. However, by this time all the gas entrapped ininlet chamber 105 has either passed previously through biological filterelement 119 or through vent filter element 117 and accomplished one ofthe objects of the invention.

Referring now to FIGS. 14-19, the construction of the inlet section 101of the biological fluid filter 100 may be clearly understood. Thebiological fluid filter 100 includes an inlet section 101 which isbonded to an outlet section 102 by a seal 130. The seal 130 ispreferably an ultrasonic seal. It can be understood by those skilled inthe art that other seals such as heat seals, adhesive seals, or anyother air tight seal may be used.

Inlet section 101 includes a recessed top wall 131, and down standingside walls 132 extending around the periphery of the recessed top wall131. A down standing peripheral ridge 133 extends around the peripheryof the down standing side wall 132 and forms a part of the mechanismwhich holds the vent filter element 117 and the biological filterelement 119 in place, as will be more fully explained hereinafter. Afirst protuberance 135 extends from the recessed top wall 131, andcarries the inlet 103 and first passage 104 as previously described.First or outlet port 104A which is in fluid communication with the firstpassage 104 can be seen in FIG. 19. A recess 136, provided by thecombination of the top surface of the recessed top wall 131 and theperipheral side walls 137 almost completely surrounds the protuberance135.

A peripheral flange 138 depends from the peripheral sidewall 137 andforms a groove 139 extending around the periphery of the inlet section101 of the biological fluid filter 100. The groove 139 forms a portionof the means by which the seal 130 between the inlet section 101 and theoutlet section 102 of the biological fluid filter 100 is formed. Aplurality of down standing ribs 142 are provided on the lower surface ofthe recessed top wall 131 for purposes to be described.

The inlet portion 101 of the biological fluid filtration device also hasan extended portion 145 which contains second passage 106 (FIG. 15) influid communication with first vent chamber 107. The same flange 138 andgroove 139 are provided in the extended portion 145 of the inlet section101 as are provided in the remainder of the inlet section 101, so thatthe inlet section 101 will properly mate with the outlet section 102 tobe described. A circular ridge 147 is provided about the first ventchamber 107 to aid in holding the vent filter, as will be furtherdescribed.

Referring now to FIGS. 15-17 and 20-21, the construction of the outletportion 102 of the biological fluid filter 100 will be clearlyunderstood. The shape of the outlet section 102 of the biological fluidfilter 100 is complimentary in shape to the inlet section 101 so thatthe inlet section 101 may act as a closure to the outlet section 102, orvice versa. It can easily be understood by those skilled in the art thatthe biological fluid filter 100 may be of any desired shape, such as thegenerally oval shape thus far described, the diamond shape of themodification shown in FIG. 22 or 24, or any other desired shape. Similarto the inlet section 101, the outlet section 102 of the biological fluidfilter 100 has a bottom wall 150 and upstanding sidewall 151. The top ofthe upstanding sidewall 151 fits into the groove 139 in the inletportion 101, and is preferably sonically welded to form the seal 130. Asecond protuberance 154 is provided on the exterior portion of thebottom wall 150 and carries the third passage 111, fourth passage 113,and a portion of the vent chamber 110. A second circular ridge 155,complimentary in shape to the circular ridge 147, is provided. Theprotuberance 154 covers a portion of the extended portion 156 of theoutlet portion 102 of the biological fluid filter 100.

As seen in FIG. 16, a further plurality of ribs 142 is provided on theinterior surface of the bottom wall 150 to help support the biologicalfilter element 119 and provide flow in the second or outlet chamber 115of the biological fluid filter 100. An upstanding ridge 157 is providedin a spaced apart relationship to the upstanding sidewall 151. As withthe circular ridges 147 and 155 when the outlet portion 22 and the inletportion 21 are in mating relationship, the down standing ridge 133 andthe upstanding ridge 157 will be in a 180° opposed relationship. As canbe seen in FIG. 15 these ridges will provide the pinch seals 160 for thevent filter element 117 and the biological filter element 119. Anultrasonic weld ridge 158 is provided to separate vent filter 117 andbiological filter element 119, and to provide additional support for thebiological fluid filter 100.

Referring to FIGS. 22 and 23, there is shown a modification of thebiological fluid filter 100 previously described. In this modificationof the invention, the biological fluid filter 100 has a housing 163,which may be constructed in a manner similar to that just described, ormay be constructed by other means well known in the art. The housing hasan inlet 164 to which a biological fluid container of the type wellknown in the art would be in fluid communication during operation. Thehousing 163 also has an outlet 165 through which the filtered fluidpasses. The outlet 165 would be in fluid communication with a biologicalreceiving container (not shown).

A filter element 166 would be sealingly mounted within the housingbetween inlet 164 and outlet 165. In this modification of the biologicalfluid filter 100, instead of there being a separate and distinct ventfilter element 117, the vent filter element 167 is embedded in thebiological fluid filter element 166 i.e., the filter medium is dividedinto two or more sections. The biological filter element 166 may be madeof a liquiphilic filter medium, and the embedded vent filter element 167may also be made of a liquiphilic filter medium, surrounded by a solidor liquiphobic barrier 168. In operation, this modification of thebiological fluid filter would operate in a similar manner to that justdescribed because of the liquiphilic nature of the biological filterelement 166, until the element was completely saturated. As the bloodwas rising in the inlet chamber 161, any entrapped gas would passthrough the embedded vent filter element 167 until the level of theblood surpassed the solid or liquiphobic barrier 168. At this time,virtually all of the entrapped gas would be downstream of the biologicalfilter element 166, the element would be completely saturated, and bloodwould now freely flow into the outlet chamber 162.

Another modification of the biological fluid filter 100 is shown inFIGS. 24 and 25. As before, there is a filter housing 163 having aninlet 164 communicating with an inlet chamber 161, and an outlet 165communicating with an outlet chamber 162. In this modification of theinvention, the biological filter element 166 has a first embeddedliquiphilic gas vent 167 surrounded by a solid barrier 168, and a secondembedded liquiphobic gas vent 173 i.e. the filter medium is divided intotwo or more sections, separated form each other, in this case, threesections.

In operation, a biological fluid container known in the art (not shown)will be in fluid communication with inlet 164. As blood is released fromthe biological fluid container it will flow into the inlet chamber 161and come into contact with the bottom of the biological fluid filterelement 166. Since filter element 166 may be a liquiphilic porousmedium, the blood level may wick up in the liquiphilic porous medium 166faster than the level in the chamber 161. The blood will not passthrough the liquiphobic second embedded gas vent 173. The secondembedded gas vent 173 will have no effect on the operation of thebiological fluid filter 100 while the liquid level continues to rise ininlet chamber 161. However, the difference between the embodiment of theinvention shown in FIGS. 22 and 23, and 24 and 25, becomes apparent whenall of the blood has been released from the biological filter containerand the level starts dropping in the inlet chamber 161. The vent filterelement 167 will stay wetted out as the level in the inlet chamber 161drops because of the blood present in the outlet chamber 162. However,as the level in the inlet chamber 161 continues to drop it will dropbelow the level of the liquiphobic second embedded gas vent 173. Sincegas vent 173 did not wet out, when the blood level drops, air will passfrom the inlet chamber 161 through the second embedded gas vent 173, andaid in draining the filter element 166, as well as the outlet chamber162, through the outlet 165.

Therefore, by carefully studying the problems present in prior artbiological filtration fluid systems; I have developed a novel method andapparatus for biological fluid filtration.

In accordance with the provisions of the patent statutes, the presentinvention has been described in what is considered to represent itspreferred embodiment. However, it should be noted that the invention canbe practiced otherwise than as specifically illustrated and describedwithout departing from its spirit or scope.

1. An open circuit fluid filtration system including: a) a filtrationdevice, said filtration device having a filter media dividing saidfiltration device into an upstream side and a downstream side, b) astorage container for holding filtered fluid, c) a second conduitconnected between the downstream side of said filtration device and saidstorage container, d) a second vent line in fluid communication with theatmosphere and connected directly to the downstream side of saidfiltration device, e) a flexible fluid container, f) a first conduit influid communication with said flexible fluid container, g) a first ventline in fluid communication with said first conduit and having an outletopen to atmosphere at a sufficient height so that a fluid being filtereddoes not exit out of the first vent line, and having a U-shaped portionwhich prevents gas entry into said fluid filtration system until adesired amount of fluid has exited said flexible fluid container, h) anupstream gas inlet housing in fluid communication with said first ventline, and i) a downstream gas inlet housing in fluid communication withsaid second vent line, said upstream gas inlet housing and saiddownstream gas inlet housing contained in a single inlet device.
 2. Afluid filtration system including: a) a filtration device, saidfiltration device having a filter media dividing said filtration deviceinto an upstream side and a downstream side, b) a fluid container, c) afirst conduit in fluid communication with said fluid container and theupstream side of the filtration device, d) a first vent line in fluidcommunication with said first conduit and having an outlet at asufficient height so that a fluid being filtered does not exit out ofthe first vent line, and having a u-shaped portion which prevents gasentry into said fluid filtration system until a desired amount of fluidhas exited said fluid container, e) a storage container for holdingfiltered fluid, f) a second conduit connected between the downstreamside of said filtration device and said storage container, g) a secondvent line in fluid communication with the downstream side of saidfiltration device and selectively open to atmosphere, h) an upstream gasinlet housing in fluid communication with said first vent line, and; i)a downstream gas inlet housing in fluid communication with said secondvent line, said upstream gas inlet housing and said downstream gas inlethousing contained in a single inlet device.